Barack Obama gained a burst of momentum from his landslide victory in the South Carolina primary on Saturday and an expected endorsement today from Democratic Sen. Edward M. Kennedy. But now, the Illinois senator faces a monumental contest that does not play to his strengths.

In eight days, on Feb. 5, Obama and his principal rival, New York Sen. Hillary Rodham Clinton, face off in the contest dubbed Super Tuesday, the biggest day of presidential primary voting in U.S. history. Twenty-two states hold Democratic primaries or caucuses that day, spanning political terrain from California to Massachusetts, from Latino communities in the West to majority-black cities in the East, a mix of states that includes some of the nation's most expensive television advertising markets.

Super Tuesday is a particular challenge for Obama, who trails Clinton in most national polls. Three of the biggest states voting -- New York, New Jersey and Connecticut -- are in Clinton's backyard; a fourth, Arkansas, was her home before her husband was elected president. Those states account for one-quarter of the delegates to be awarded that day.

In California, which holds the biggest cache of delegates, polls show Clinton has a commanding -- although narrowed -- lead over Obama.

Moreover, the multi-state field of Super Tuesday does not play to Obama's signature strength: his ability to win over voters in live town-hall settings, using his soaring oratory and personal charm. That worked for him in Iowa, where many voters met him personally more than once. In a national campaign, by contrast, most voters' only contact with Obama will be through advertising and surrogates.

Still, the Obama campaign has a strategy for countering Clinton's big-state advantage -- one built in part on the Democratic rules for how delegates are awarded.

Rather than a winner-take-all system, in which the candidate who gets the most votes in a state claims all the delegates, Democrats have elaborate rules that award delegates in proportion to each candidate's share of the vote.

That means even a Clinton stronghold like New Jersey may produce some delegates for Obama -- and it explains why Obama visited Jersey City this month, weeks before New Jersey was set to vote, where a crowd of about 4,500 lined up to hear him.

Despite early predictions that the primary contest would be resolved by Feb. 5, both the Clinton and Obama campaigns now assume that neither candidate will lock up the nomination that day. Even a Clinton strategist predicts that the two will emerge with very close delegate counts.

In all, nearly 1,700 delegates will be awarded on Super Tuesday, a big boost toward the 2,025 needed to clinch the Democratic nomination. California will award 370 delegates that day, or about 22% of the delegates at stake. Republicans will hold their own nominating contests Feb. 5, most in the states where Democrats are voting.

The last two days have strengthened Obama's hand.

His 28-point victory margin over Clinton on Saturday in South Carolina was far wider than most predicted, giving Obama energy and new funds. His campaign raised $500,000 through its website in the hour after the South Carolina polls closed, according to a spokesman. Obama carried 55% of the vote in South Carolina, compared to 27% for Clinton and 18% for John Edwards.

On his way to winning South Carolina, Obama drew support from about 80% of African American voters, exit polls showed. That leaves him positioned to do well Feb. 5 in states such as Georgia, Alabama and Tennessee, which have large populations of African American Democrats.

The biggest prize among these states will be Georgia, where blacks could make up more than 40% of the Democratic primary vote, and 87 delegates are at stake. Obama has been endorsed by Atlanta's black mayor, Shirley Franklin, and recent polls show he has an edge over Clinton in the state.

Obama argued Sunday that his South Carolina victory, in which he won about a quarter of white voters, showed that he appeals to all races. While some think that "if you get black votes, you can't get white votes," his success in South Carolina proved that untrue, Obama told a crowd of more than 9,000 at the University of Alabama at Birmingham.

Kennedy, the Massachusetts senator and one of the Democratic Party's most senior figures, will campaign for Obama and help him shore up support among Latino voters, said someone close to the endorsement announcement.

Latino voters are a mainstay of Clinton's base, and they have a large presence in California, Arizona and several other states that vote Feb. 5. The Obama campaign believes that Kennedy will carry influence among Latinos in part because of his prominent role in calling for an overhaul of immigration laws that includes a path to citizenship for undocumented workers.

Kennedy is expected to endorse Obama at a rally at American University in Washington. News of Kennedy's decision came the day that his niece, Caroline, backed Obama in a New York Times opinion article in which she said Obama could inspire Americans as did her father, President Kennedy. Caroline Kennedy is scheduled to appear at today's rally as well.

Obama already had a leg up on the third-largest delegate prize of Super Tuesday: his home state of Illinois. And he has built organizations in the six states that are holding caucuses rather than primaries: Alaska, North Dakota, Colorado, Minnesota, Kansas and Idaho. The caucus format, which requires voters to attend meetings to express support for their candidate, plays to the Obama campaign's strength in grass-roots organizing that it honed in the Iowa caucuses.

A Clinton advisor, who asked not to be named when discussing campaign strategy, conceded Obama's strength in the caucus states but said that far fewer delegates were to be had there, compared to the populous states that form Clinton's base.

Still, with a visit to Florida, Clinton signaled Sunday that she is serious about gathering all possible delegates for the nomination fight.

The Democratic National Committee last year said it would not seat delegates from Florida as punishment for the state's decision to leapfrog other states and set its primary election earlier in the calendar than party rules allowed. Democratic candidates agreed not to campaign there.

Florida's election will proceed Tuesday, and Clinton anticipates winning. On Sunday, she repeated her call for the party to revoke its punishment and seat Florida's delegates at the national nominating convention this summer.

"I'm going to try to seat the Florida delegates," Clinton said at a news conference in Tennessee. "I've said that the people of Florida deserve to be represented in the process of picking a president for the Democratic Party."

Clinton later flew to Florida for three fundraising events and promised to return Tuesday night after the votes are counted. "I want the voters in Florida to know that I hear them, that I deeply care about their problems," she said at the news conference.

While her words and fundraising trip were bound to attract media attention in Florida, Clinton was not scheduled to take part in campaign rallies in the state, sticking to a pledge that she and other Democratic candidates made not to publicly campaign there.

Obama's campaign cast the Florida race as meaningless. "If the Clinton campaign's Southern strength rests on the outcome in a state where they're the only ones competing, that should give Democrats deep pause," said Obama spokesman Bill Burton.

In California, Clinton has led in the polls from the beginning, but her margin has narrowed. In October, the Field Poll found her ahead by 25 points; in the most recent Field Poll, the margin shrank to 12 points.

Clinton's strongest groups form the bulwark of the state's Democratic party: women, lower-income people and Latinos. African Americans are strong for Obama, but they represent only 7% of the electorate, according to the Field Poll.

Endorsed in California by Sen. Dianne Feinstein and Los Angeles Mayor Antonio Villaraigosa, Clinton is campaigning as the establishment candidate. But with Kennedy's expected endorsement of Obama, it's clear the political establishment isn't ready to fall in behind one candidate yet.